The present invention relates to semiconductor devices and manufacturing methods thereof, and more particularly, to a semiconductor device including a photoelectric conversion element, such as a photodiode, and a manufacturing method thereof.
A semiconductor device (solid-state image sensing element) for an image sensor has a plurality of photoelectric conversion elements, such as photodiodes, formed over a semiconductor substrate with a spacing therebetween. In order to suppress a leak current flowing between a pair of adjacent photodiodes, the semiconductor device has an isolation insulating film for element isolation formed between the pair of photodiodes. When forming the isolation insulating film, a number of damage layers are formed. Via the damage layer, a fine leak current called dark current might flow between the pair of adjacent photodiodes in some cases. The leak current becomes noise to the solid-state image sensing element, which reduces the performance of the solid-state image sensing element. To suppress this phenomenon, a current blocking region called a guard ring is provided in the vicinity of the isolation insulating film.
The structure with the guard ring in contact with the isolation insulating film is disclosed, for example, in Japanese Unexamined Patent Application Publication No. 2012-28380 (Patent Document 1).